An integrated circuit formed on a semiconductor substrate includes a plurality of active and passive components, such as resistors, inductors, capacitors, transistors, amplifiers, and so on. The above components are manufactured in accordance with a design specification that defines an ideal physical or electrical characteristics (e.g., resistance, inductance, capacitance, gain, etc.) of the components. In general, some components cannot be confirmed to meet their design specifications after they are integrated into the integrated circuit, although they are expected to be confirmed. In other words, a stand-alone copy of each of the components above-mentioned is independently manufactured on a wafer by using the same processes as it is manufactured in the integrated circuit, which has the same physical/electrical characteristics as it is in the integrated circuit. And it is assumed that the physical/electrical characteristics obtained by measuring the stand-alone copy are equivalent to its physical/electrical properties in the integrated circuit.
During the test, the stand-alone copy called a device-under-test (DUT), is electrically connected to leads and test pads. Further, the leads and the test pads are electrically connected to an external test device, e. g., a vector network analyzer (VNA). The VNA can measure various parameters of the DUT characterizing its electrical characteristics, e. g., S parameters (i.e. scattering parameters), Y parameters (i.e. admittance parameters), Z parameters (i.e. impedance parameters), H parameters, and etc. When the DUT is used in high-frequency microwave circuits, the scattering parameters (i.e. S parameters) are usually used to characterize the electrical characteristics of the DUT. However, due to the parasitic effects generated by the leads and the test pads (e. g., resistance values, capacitance values and inductance values of the leads and the test pads) are also contained in the various parameters of the DUT during the test, a de-embedding method is usually utilized to subtract the parasitic effects, so as to obtain the actual electrical characteristics of the DUT.
In order to obtain the real test data of the DUT, a lot of de-embedding methods are proposed, such as an open de-embedding method proposed in the paper of “C. H. CHEN and M. J. DEEN, High frequency Noise of MOSFETs I Modeling. Solid-state Electronics Vol. 42, No. 11, pp. 2069-2081, 1998”, and an open-short de-embedding method proposed in the paper of “K. Aufinger and J. Bock, A Straightforward Noise De-embedding Method and Its Applications to High-Speed Silicon Bipolar Transistors, Proceedings of ESSDERC 96, pp. 957”, which are widely used in the prior art. However, the open de-embedding method can only remove the parasitic capacitance of the test pads, while the open-short de-embedding method ignores the parasitic capacitance effect on the noise although it not only can remove the parasitic capacitance of the test pads, but also can remove the parasitic resistance and the parasitic inductance of the metal leads. With the continues decreasing of the device size and the continues increasing of application frequency, the effect of the parasitic capacitance of the metal leads becomes very important. Therefore, an open-thru de-embedding method is proposed by the paper of “C. H. CHEN and M. J. DEEN, A General Procedure for High-Frequency Noise Parameter De-embedding of MOSFETs by Taking the Capacitive Effects of Metal Interconnection into Account, IEEE, Conference on Microelectronic Test Structures, Vol. 14, March 2001” to remove the parasitic capacitance of the metal leads.
More de-embedding methods are further disclosed in china patent publication No.CN100541224, No.CN101943739B, No.CN103063999A, and No. CN13066773B and china patent application No. CN13050479A.
Take the prior open-thru de-embedding method as an example, the de-embedded structure is shown in the FIG. 1, including a DUT structure 1, an open-only de-embedding test structure 2, a first thru-only de-embedding test structure 3A, and a second thru-only de-embedding test structure 3B. Wherein, the DUT structure 1 comprises a RF device 11, a signal input pad 51, a signal output pad S2, and four grounded pads G1, G2, G3 and G4. The signal input pad 51 is connected to an input end of the RF device 11 by a metal lead 12, and the signal output pad S2 is connected to an output end of the RF device 11 by a metal lead 13. The four grounded pads are connected to each other by a metal lead 14, and also connected to the grounded terminal of the RF device 11. The signal input pad 51 and the signal output pad S2 are arranged on a first straight line, and are occupied on two ends of the first straight line. A second straight line and a third straight line are symmetrically arranged on both sides of the first straight line and both are parallel to the first straight line. There are four grounded pads arranged on two ends of the second straight line and the third straight line, respectively. Specifically, the grounded pad G1 and the grounded pad G2 are respectively occupied on two ends of the second straight line, while the grounded pad G3 and the grounded pad G4 are respectively occupied on two ends of the third straight line And the grounded pads G1 and G3 are aligned with the signal input pad S1 in a direction perpendicular to the first straight line, while the grounded pads G2 and G4 are aligned with the signal output pad S2 in a direction perpendicular to the first straight line.
The open-only de-embedding test structure 2 is get by removing the RF device 11 and the metal leads 12 and 13 from the DUT structure 1.
The first thru-only de-embedding test structure 3A is get by removing the RF device 11 from the DUT structure 1. And the signal input pad S1 and the signal output pad S2 are connected together by a metal lead 12a, which has the same length and width with the metal lead 12. The grounded pads G1 and G2 are connected together by a metal lead, and the grounded pads G3 and G4 are connected by another metal lead, while the grounded pads G1 and G2 on the second straight line and the grounded pads G3 and G4 on the third straight line are not connected together.
The second thru-only de-embedding test structure 3B is get by removing the RF device 11 from the DUT structure 1. And the signal input pad S1 and the signal output pad S2 are connected together by a metal lead 13a, which has the same length and width with the metal lead 13. The grounded pads G1 and G2 are connected together by a metal lead, and the grounded pads G3 and G4 are connected by another metal lead, while the grounded pads G1 and G2 on the second straight line and the grounded pads G3 and G4 on the third straight line are not connected together.
Referring to the FIG. 2, which is a flow chart of a de-embedding calculation of a prior open-thru de-embedding method. Firstly, a first scattering parameter SDUT of the DUT structure 1, a second scattering parameter SPAD of the open-only de-embedding test structure 2, a third scattering parameter STHRU1 of the first thru-only de-embedding test structure 3A, a forth scattering parameter STHRU2 of the second thru-only de-embedding test structure 3B, and noise parameters of the DUT structure 1 are obtained by testing. Wherein, the noise parameters of the DUT structure 1 include a first minimum noise figure NFminDUT, a first optimum source impedance YoptDUT comprised of a real part Gopt and an imaginary part Bopt, and a first equivalent input impedance RnDUT. Secondly, a de-embedding calculation is used to obtain noise parameters of the RF device of the DUT structure 1 according to the above test results of scattering parameters and noise parameters.
Specifically, the prior de-embedding calculation includes the following steps:
Step 1: transferring the second scattering parameter SPAD into a second admittance parameter YPAD of the open-only de-embedding test structure 2, and further transferring the received second admittance parameter YPAD into a second ABCD parameter APAD, wherein the formula of the transformation of the second admittance parameter YPAD into the second ABCD parameter APAD could refer to
      A    PAD    =      [                            1                          0                                                  Y            PAD                                    1                      ]  shown in the FIG. 3. The RF device shown in the FIG. 3 is a MOSFET device, wherein, the port 1 is an input terminal, which the source is grounded and the gate is signal input end, and the port 2 is an output terminal, which the source is grounded and the drain is the signal output end.
Step 2: transferring the third scattering parameter STHRU1 into a third ABCD parameter ATHRU1 of the first thru-only de-embedding test structure 3A and transferring the forth scattering parameter STHRU2 into a forth ABCD parameter ATHRU2 of the second thru-only de-embedding test structure 3B.
Step 3: calculating an ABCD parameter AIN of the input end of the DUT structure 1 according to an ABCD parameter ATHRU1′ and the second ABCD parameter APAD, shown in the FIG. 3, wherein the ABCD parameter ATHRU1′ is the ABCD parameter of the metal lead 12a in the first thru-only de-embedding test structure 3A and is obtained by removing the both second ABCD parameter APAD from the third ABCD parameter ATHRU1 of the first thru-only de-embedding test structure 3A. Because the metal lead 12 and metal lead 12a are identical, the ABCD parameter ATHRU1′ is also equal to the ABCD parameter of the metal lead 12 in the DUT structure 1. Calculating an ABCD parameter AOUT of the output end of the DUT structure 1 according to an ABCD parameter ATHRU2′ and the second ABCD parameter APAD, wherein the ABCD parameter ATHRU2′ is the ABCD parameter of the metal lead 13a in the second thru-only de-embedding test structure 3B. Because the metal lead 13 and metal lead 13a are identical, the ABCD parameter ATHRU2′ is also equal to the ABCD parameter of the metal lead 13 in the DUT structure 1.
Step 4: transferring the first scattering parameter SDUT into a first ABCD parameter ADUT of the DUT structure 1. Further, calculating a fifth ABCD parameter ATRANS of the RF device of the DUT structure 1 according to the first ABCD parameter ADUT, the ABCD parameter AIN of the input end and the ABCD parameter AOUT of the output end. And calculating a first correlation matrix CADUT according to the minimum noise figure NFminDUT, the optimum source impedance YoptDUT and the equivalent input impedance RnDUT. And calculating a correlation matrix CZIN of the input end of the DUT structure 1 according to the ABCD parameter AIN of the input end, and further deriving out a second correlation matrix CAIN. And calculating a correlation matrix CZOUT of the output end of the DUT structure 1 according to the ABCD parameter AOUT of the output end, and further deriving out a third correlation matrix CAOUT.
Step 5: calculating a correlation matrix CA of the RF device according to the input end ABCD parameter AIN, the fifth ABCD parameter ATRANS, the first correlation matrix CADUT, the second correlation matrix CAIN, and the third correlation matrix CAOUT. And finally deriving out the noise parameters of the RF device, including a second minimum noise figure NFmin, a second optimum source impedance Yopt, and a second equivalent input impedance Rn, according to the correlation matrix CA.
Above methods have improved the accuracy of the de-embedding and increased the frequency range applicable to the de-embedding results.
However, the above-proposed methods are based on the uses of different sub-circuit models to simulate the parasitic factors introduced by the test structure. With the increasing frequency, the simple parasitic element equivalent circuit model is no longer effective at high frequency. Therefore, the corresponding de-embedding strategy is proposed basing on more complex sub-circuit equivalent model. However, the prior technologies mainly focus on the study about the embedded steps of an embedded method and illustrate the progress effect by theoretical analysis, but ignore the evaluation of the de-embedding accuracy and the applicable range.